1. Field of the Invention
The present invention relates to a photomask correction apparatus for correcting defects in photomasks employed, for example, in photolighographic steps for photoconductors.
2. Description Of Related Art:
A photomask is used when, for example, exposing a pattern of a photoresist in a photolithographic step of a semiconductor process. Namely, a desired pattern is exposed by irradiating a film to be subjected to processing, such as a photoresist, with light via a photomask.
A photomask is made by forming a light blocking film pattern on a surface of a transparent substrate. Portions on which the light blocking film is formed then block out light, and these portions of the photoresist etc. are therefore not exposed to light.
There are, however, cases where defects are formed at the surface of the transparent substrate while making the photomask. Such defects consist of clear defects and opaque defects. Clear defects are where a light blocking film is not formed in a place where it was intended to form a light blocking film. On the other hand, opaque defects are where a light blocking film is not formed where it was intended to form the light blocking film.
For example, a focussed ion beam apparatus can be employed as an apparatus for correcting clear defects and opaque defects.
Conventionally, when correction is carried out using this kind of correction apparatus, an operator first designates a region of the photomask to be observed and makes observations on a monitor. When a defect appears, an operator designates coordinates of the region where the defect is formed.
When a defect is a clear defect, the operator operates the correction apparatus so that light blocking film material is deposited on the clear defect region. When a focussed ion beam apparatus is used as a correction apparatus, a light blocking film can be formed on the clear defect region by blowing raw material gas over the photomask while irradiating the clear defect with an ion beam.
On the other hand, when a defect is an opaque defect, the operator operates the correction apparatus so that light blocking film material is removed from the opaque defect region. When a focussed ion beam apparatus is used as a correction apparatus, the opaque defect can be etched away by blowing etching gas over the photomask while irradiating the opaque defect with an ion beam.
It is therefore possible to make a highly reliable photomask by correcting defects in this manner.
With related photomask correction technology, it is necessary for an operator to input the coordinates of regions where defects are formed into the photomask correction apparatus using a monitor.
However, when a normal region of a light-blocking film and a defect overlap, it is difficult to discern the border of the normal region and the defect region on a monitor. This has the drawback that related photomask correction technology places an enormous workload on the operator.
In order to resolve the aforementioned problems, it is an object of the invention to provide a photomask correction apparatus capable of alleviating the workload placed on an operator at the time of correcting defects.
The photomask correcting apparatus of this invention for correcting defects in light blocking film formed on a surface of a photomask comprises storage means for storing positional relationships between the defects of the photomask and normal regions as one type or a plurality of types of patterns; sensing means for generating image information for the photomask; and determining means for determining a region for the defect using the patterns inputted from the input means and the image information inputted from the sensing means.
According to this invention, it is possible to identify a boundary line between a normal region and a defect using a pattern indicating the positional relationship of the blocking film defect and a normal region, and image information, and thus alleviate the workload involved in correcting defects.